Verified answer

x²-2x =15.......(x=y)

x²-2x-15=0

Δ=b²-4.a.c =4+60=64 => √Δ=8

x=(-b±√Δ)/2a

x'=(2+8)/2 = 10/2 = 5

x''=(2-8)/2 = -6/2 = -3

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2-A aresta de um cubo mede a=3√3 cm, calcule:

a)sua diagonal => D= a.√3 = 3√3. √3 = 3√9 = 3.3 = 9 cm

b)a area total => At= 6.a² = 6.(3√3)² = 6.(27) = 162 cm²

c)o seu volume => V= a³ = a².a = (3√3)².(3√3) = 27.(3√3) = 81√3 cm³

x² - 2x = 15

x² - 2x - 15 = 0

(x - 5)*(x + 3) = 0

x = 5

x = -3

pronto